1. Technical Field
The present invention relates to multifilament crimped yarn comprising an aliphatic polyester and methods for producing thereof, and to carpets that are manufactured by using the crimped yarn. More specifically, the present invention relates to multifilament yarn which is suitably employed for fibers for carpets, having improved biodegradability in the nature world and having improved mechanical properties such as light fastness, durability, bulkiness and so on, and improved tactile impression, to methods for manufacturing thereof, and to carpets that comprises the crimped yarn.
2. Background Art
Aliphatic polyesters typified by polylactic acid recently attract much attention as materials involving reduced load on the environment. The reasons are: the raw materials thereof do not necessarily require petroleum, and therefore it helps reducing total CO2 emission in view of the production through the disposition thereof; and the material is broken down when it is taken within soil due to its biodegradability, and thus it helps reducing wastes.
Aliphatic polyesters have been used for industries such as agricultural materials, civil engineering materials and so on. Aliphatic polyesters are also employed for fiber materials, and related technologies for obtaining aliphatic polyester fibers by spinning aliphatic polyesters are disclosed (see, for example, Japanese Unexamined Patent Application Publication No. 12-220032, 12-220054 and so on).
On the other hand, a large number of the carpets are used and consumed for helping the comfortable modern life, and also scrapped, and since the carpets are generally bulky and thus difficult to be collected, there are problems of increasing the amount of wastes thereof. Synthetic fibers conventionally used for the carpet such as polyamide fiber, polyolefin fiber, polyester fiber and the like have considerably high durability in the nature environment and are very difficult to naturally broken down, and therefore such fibers have a drawback of semi-permanently remaining unless they are burned.
According to the background described above, an attempt of employing a biodegradable material for the pile of the carpet (see, for example, WO 00/65140 and so on). However, in general, aliphatic polyester multifilament crimped yarn has a tendency of being readily wear out and/or excessively crimped, and when the yarn is thermally processed at higher level during the crimping process for the purpose of obtaining higher crimp, the mechanical strength of resultant yarn is subject to decrease, and therefore it was difficult to be compatible the mechanical strength with the crimp characteristics.
In this reason, multifilament crimped yarn comprising aliphatic polyester having characteristics that include improved bulkiness and improved tactile impression suitable for the carpet has not been obtainable at the present time.
The object of the present invention is to provide an aliphatic polyester multifilament crimped yarn having characteristics, in which the bulkiness and the tactile sensation suitable for the carpet and the mechanical strength required for the carpet can reconcile, and being biodegradable. In addition, the present invention also provides carpets formed by using thereof and methods for producing thereof.
Specifically, the present invention provides a multifilament crimped yarn comprising an aliphatic polyester having a melting point of equal to or higher than 130xc2x0 C., and more specifically an aliphatic polyester multifilament crimped yarn for the carpets characterized in having crimp elongation rate of the multifilament crimped yarn after being processed with boiling water of 3-35% and breaking strength of 1-5 cN/decitex, and carpets manufactured by using thereof, and methods for producing the aliphatic polyester multifilament crimped yarn including a step of providing crimp to drawn multifilament fiber comprising a biodegradable polymer including an aliphatic polyester as a main component by using a crimp-providing apparatus that utilizes heated air.